Stickyb,
Don't know for sure but your situation was possibly significantly different from the EAAC incident because of the geographical position.
The drift down height for three engines may have put the flight below the minimum safe altitude for continuing over the mountains of Afghanistan or the foothills of the Himalayas. Also, someone me me able to confirm, there may be a minimum allowable altitude for civil flights to cross Afghanistan (if the flights routes over Afghanistan, that is).
The return all the way to LHR (still a bl**dy long way on three engines according to some people who have posted above) would be because of the maintenence facilities available to Cathay.